Die casting refers to a process in which molten metal is introduced into a mold or set of dies to form cast items having shapes defined by one or more hollow regions in the dies. Many casting operations utilize expendable cores that are positioned in the casting chamber such that the molten metal flows around the core. After solidification of the cast metal part, the core can be removed to reveal an undercut or hollow region in the resulting metal part. This process is typically referred to as casting with expendable cores. Expendable cores can be formed from a wide array of materials. Many such cores are formed from foundry sand dispersed with a resinous binder.
As molten metal flows into the casting chamber, air or other gases residing therein are displaced and must be directed out of the chamber. If gases remain in the chamber during a casting operation, the gases can result in voids, depressions, or other structural discontinuities in the cast metal item. Accordingly, artisans have incorporated a wide array of vents and venting systems in casting equipment and casting dies to remove such gases from the casting chamber.
A problem associated with casting molten metals, and particularly when using expendable sand cores mixed with resinous binder, is that the extremely high temperature metals frequently generate gases within the casting chamber. This is largely due to contact between the molten metal and the binder in the core and/or other volatilizable materials exposed within the casting chamber. The extremely hot molten metal rapidly vaporizes these materials(s) within the chamber.
The volatilized material(s) or gases, are typically removed from the casting chamber by a venting system. However, as the gases exit the casting chamber and travel through the vents, materials in the gases may deposit on the interior vent surfaces. These deposits may originate from numerous sources, however they are typically volatilized binder from expendable cores and/or from other materials within the casting chamber. If the resulting deposits on vent surfaces are not periodically removed, the vents can become blocked or flow therethrough can become restricted. Blocked or restricted flow in one or more vent passages can then result in the previously described structural discontinuities in the cast items if gases are not readily directed out of the chamber. Thus, many manufacturing facilities require frequent maintenance of their casting equipment, and particularly, require removal of deposits or other buildup along interior vent surfaces.
Accordingly, a need exists for a strategy by which deposit of materials in vent passageways can be prevented or at least significantly reduced. Related to this, it would be beneficial to provide a casting system which eliminated or at least significantly reduced the tendency for such deposits in vents. In addition to avoiding the potential of poorly formed cast items, prevention of such deposits would also reduce the extent of maintenance otherwise required.